Patterning of the materials used in the semiconductor industry is one of the major steps in fabrication of microelectronic devices, integrated circuits and optoelectronic devices including semiconductor lasers. Conventionally known methods of patterning comprise selectively masking a semiconductor material with a photoresist or any other masking material, followed by etching. Known etching methods include selective wet chemical etching, or dry etching, e.g. plasma and reactive ion etching. (E.g., see Van Nostrand's Scientific Encyclopedia, 7th Edition, Ed. by Douglas and Glenn Considine, NY, 1989, pp. 1851-1852.) Anisotropic etching processes are known for defining microscopic structures of sub-micron dimensions.
Nevertheless, there are limitations associated with known etching processes, for example, in etching multilayer structures of different materials, because etchants are material specific and often only one layer of a particular material can be etched with a specific etchant. Thus etching through several layers of different materials may require numerous steps and be time consuming and costly. Control of etch rates, sidewall and perimeter profiles may present challenges requiring careful control of etch parameters, which is also necessary to reduce unwanted etch damage, and etch residues and edge distortions and provide reproducible and consistent etch processes. Etching of deep structures may be time consuming, or require multiple steps. Endpoint control is required to prevent underetching and overetching, undercutting and other distortions. Etchants may include hazardous or reactive materials requiring special handling expense for safe handling, and high purity materials to prevent contamination of sensitive semiconductor structures. Furthermore, there are some materials which cannot be readily etched using conventional techniques, e.g. some dielectrics such as lithium fluoride, lithium niobate.
Therefore a need exists for development of alternative methods for patterning brittle materials, and particularly semiconductor materials, which would for example avoid multiple step etching for patterning through multi-layer structures, and allow rapid deep patterning, and be applicable to an extended list of materials.